The subject matter disclosed herein relates to Rankine cycle systems and, in particular, to arrangements of heat pipes for transferring heat from a waste heat source to an organic Rankine cycle evaporator.
Organic Rankine cycle (“ORC”) systems typically utilize working fluids (e.g., pentane, ammonia, etc.) with relatively low evaporation and condensation temperatures (i.e., lower than water). Such non-water systems allow for transforming heat (e.g., waste heat) from relatively lower temperature sources into useful work, for example, rotary power to drive generators. Sources of available low-temperature waste heat include the exhausts of coal-fired boilers (e.g., exhaust flows located upstream of a wet scrubber), cement and other kiln exhausts, glass furnaces, and other continuous industrial thermal processes. One alternative is to place the evaporator of the ORC system directly in the hot gas path. Another is to use a hot oil loop, with the hot oil exchanger located in the hot gas path.
However, the installation of heat exchangers directly in the hot gas paths of ORC systems poses concerns for flammability and/or toxicity of organic working fluids in the event of leaks in the heat exchanger. Also, the use of hot oil loops that heat the oil via a heat exchanger in the hot gas path and evaporate the ORC working fluid in an external heat exchanger is commonly found in various industrial usages, but is relatively expensive and involves installation of relatively heavy components.